This invention relates to a hydraulic pressure amplifier or intensifier which receives pressure fluid from a low pressure pump and increases the pressure of the fluid automatically to a desired magnitude in order to operate a utilization device. One specific type of utilization device which the amplifier may serve is a single-acting hydraulic actuator having a rod which is advanced in one direction when pressure fluid is admitted into one end of a cylinder. When the pressure fluid is released from the cylinder, a spring returns the rod in the opposite direction.
More specifically, the invention constitutes an improvement over the amplifier disclosed in Lapp U.S. Pat. No. 3,952,516. In that amplifier, a rotary hydraulic motor drives a high pressure pump for boosting the pressure of the low pressure fluid. The motor also drives a scavenging pump which positively induces a negative return line pressure to effect a fast and positive return of the rod of the hydraulic actuator.